1. Field
One or more example embodiments relate to an apparatus for reducing an electromagnetic wave in a wireless power transmitter using a reducing coil, and more particularly, to an electromagnetic wave reducing apparatus that reduces external emission of an unnecessary harmonic, rather than a transmission frequency to transmit wireless power.
2. Description of Related Art
Wireless power transmission technology is applied to an electronic device such as a smart phone to enable wireless power supply to an electronic device beyond the limit of an existing charging scheme that supplies power using wire. Recently, for wireless power supply, the wireless power transmission technology has been applied to various electronic devices, and transmission power that may be wirelessly transmitted is increasing from several watts (W) to several kilowatts (kW).
However, as energy is transmitted wirelessly, electromagnetic wave emission into a space increases, which causes growing concerns about electromagnetic wave interference to other devices. In particular, a wireless power transmitter generates a square wave of a low frequency band in a transmission circuit and transmits the square wave to a transmission coil. The transmission coil transmits energy through a free space for wireless power transmission. A reception coil receives the energy from the free space and power is supplied through a reception circuit.
Here, the square wave of the low frequency band emits an electromagnetic wave by a harmonic component as well as a basic frequency of the square wave, and the electronic wave emission of the harmonic component is considerably great at 30 megahertz (MHz) or less. As existing electromagnetic compatibility (EMC) caused by electromagnetic wave emission, conducted emission at 30 MHz or below and radiated emission at 30 MH or above cause device malfunction. However, wireless power transmission influences device malfunction and interference by radiated emission at 30 MHz or below.
Thus, there is regulation of wireless power transmitters with respect to electromagnetic wave emission. However, the regulation only sets a radiated emission strength limit from a low frequency band except a frequency for wireless power transmission, but does not include measures to reduce an electromagnetic wave.
Accordingly, measures to reduce an electromagnetic wave are needed to reduce external emission of harmonic components.